[Patch, Fortran, pr60322, addendum] was: [Patch 1/2, Fortran, pr60322] [OOP] Incorrect bounds on polymorphic dummy array
Andre Vehreschild
vehre@gmx.de
Tue Apr 14 17:01:00 GMT 2015
Hi all,
during further testing of a big Fortran software I encounter two bugs with
class arrays, that are somehow connected to pr60322. I therefore propose an
extended patch for pr60322. Because Paul has already reviewed most the extended
patch, I give you two patches:
1. a full patch, fixing all the issues connected to pr60322, and
2. a delta patch to get from the reviewed patch to the latest version.
With the second patch I hope to get a faster review, because it is
significantly shorter.
Now what was the issue? To be precise there were two issues:
i. a pointer to a class array (CLASS_DATA(sym).attr.class_pointer == 1) was
dereferenced, which lead to an ICE (the patch for this in the delta is chunk 5
in gfc_conv_expr_descriptor, and
ii. (and this was a severe brain cracker) in chains of references consisting of
more then one class-(array)-ref always the _vptr of the first symbol was taken
and not the _vptr of the currently dereferenced class object. This occurred
when fortran code similiar to this was executed:
type innerT
integer, allocatable :: arr(:)
end type
type T
class(innerT) :: mat(:,:)
end type
class(T) :: o
allocate(o%mat(2,2))
allocate(o%mat(:,:)%arr(10)) ! This is obviously pseudo code,
! but I think you get what is meant.
o%mat(1,1)%arr(1) = 1
In the last line the address to get to arr(1) was computed using the
_vptr->size of o and not of o%mat(1,1). To fix this gfc_component_ref () now
computes the class' _vptr-ref whenever it does a _data-ref (chunk 1 of
trans-expr.c in the delta patch). The _vptr-ref is stored in gfc_se, where I
added the new member class_vptr. The gfc_se->class_vptr is then used in
array-refs (chunk 2 of trans.c) to get the size of the array elements of the
correct level.
The other chunks of the delta patch are:
- parameter passing fixes, and
- documentation fixes as requested for the version 5 of the pr60322 patch.
I hope this helps in getting the patch reviewed quickly.
Bootstraps and regtests ok on x86_64-linux-gnu/F21.
Ok for trunk -> 6.0?
Ok, for backport to 5.2, once available?
Note, the patches may apply with shifts, as I forgot to update before taking
the diffs.
Regards,
Andre
On Thu, 9 Apr 2015 14:37:09 +0200
Andre Vehreschild <vehre@gmx.de> wrote:
> Hi Paul, hi all,
>
> Paul, thanks for the review. Answers to your questions are inline below:
>
> On Sun, 5 Apr 2015 11:13:05 +0200
> Paul Richard Thomas <paul.richard.thomas@gmail.com> wrote:
> <snip>
> > + /* The dummy is returned for pointer, allocatable or assumed rank arrays.
> > + The check for pointerness needs to be repeated here (it is done in
> > + IS_CLASS_ARRAY (), too), because for class arrays that are pointers,
> > as
> > + is the one of the sym, which is incorrect here. */
> >
> > What does this mean, please?
>
> The first sentence is about regular arrays and should be unchanged from the
> original source. Then I have to check for class (arrays) that are pointers,
> i.e., independent of whether the sym is a class array or a regular pointer to
> a class object. (The latter shouldn't make it into the routine anyway.)
> IS_CLASS_ARRAY () returns false for too many reasons to be of use here. I have
> to apologize and confess that the comment was a mere note to myself to not
> return to use is_classarray in the if below. Let me rephrase the comment to
> be:
>
> /* The dummy is returned for pointer, allocatable or assumed rank arrays.
> For class arrays the information if sym is an allocatable or pointer
> object needs to be checked explicitly (IS_CLASS_ARRAY can be false for
> too many reasons to be of use here). */
>
> > + /* Returning the descriptor for dummy class arrays is hazardous,
> > because
> > + some caller is expecting an expression to apply the component refs to.
> > + Therefore the descriptor is only created and stored in
> > + sym->backend_decl's GFC_DECL_SAVED_DESCRIPTOR. The caller is then
> > + responsible to extract it from there, when the descriptor is
> > + desired. */
> > + if (IS_CLASS_ARRAY (sym)
> > + && (!DECL_LANG_SPECIFIC (sym->backend_decl)
> > + || !GFC_DECL_SAVED_DESCRIPTOR (sym->backend_decl)))
> > + {
> > + decl = gfc_build_dummy_array_decl (sym, sym->backend_decl);
> > + /* Prevent the dummy from being detected as unused if it is copied.
> > */
> > + if (sym->backend_decl != NULL && decl != sym->backend_decl)
> > + DECL_ARTIFICIAL (sym->backend_decl) = 1;
> > + sym->backend_decl = decl;
> > + }
> >
> > The comments, such as the above are often going well beyond column 72,
> > into the 80's. I know that much of the existing code violates this
> > style requirement but there is no need to do so if clarity is not
> > reduced thereby.
>
> Er, the document at
>
> https://gcc.gnu.org/codingconventions.html#C_Formatting
>
> says that line length is 80, or is there another convention, that I am not
> aware of?
>
> > In trans-stmt.c s/standart/standard/
>
> Fixed.
>
> > Don't forget to put the PR numbers in the ChangeLogs.
>
> I won't anymore, already got told off :-)
>
> > For this submission, I would have appreciated some a description of
> > what each chunk in the patch is doing, just because there is so much
> > of it. I suppose that it was good for my imortal soul to sort it out
> > for myself but it took a little while :-)
>
> I initially tried to split the submission in two parts to make it more
> manageable. One part with the brain-dead substitutions of as and array_attr
> and one with the new code. Albeit I failed to get the brain-dead part right
> and made some mistakes there already, which Mikael pointed out. I therefore
> went for the big submission.
>
> Now doing a description of what each "chunk" does is quite tedious. I really
> would like to spend my time more productive. Would you be satisfied, when I
> write a story about the patch, referring to some parts more explicitly, like
>
> "Chunk 4 of file trans-stmt.c is the heart of the patch and does this and
> that. The remaining chunks are more or less putting the data together."
>
> (This is not correct for this patch of course. Just an example.) More
> elaborate of course, but just to give an idea.
>
> Thanks again. I will commit as soon as 5.2/6.0 commit window is open.
>
> Regards,
> Andre
>
> >
> > Cheers and many thanks for the patch.
> >
> > Paul
> >
> > On 27 March 2015 at 13:48, Paul Richard Thomas
> > <paul.richard.thomas@gmail.com> wrote:
> > > Dear Andre,
> > >
> > > I am in the UK as of last night. Before leaving, I bootstrapped and
> > > regtested your patch and all was well. I must drive to Cambridge this
> > > afternoon to see my mother and will try to get to it either this
> > > evening or tomorrow morning. There is so much of it and it touches
> > > many places; so I must give it a very careful looking over before
> > > giving the green light. Bear with me please.
> > >
> > > Great work though!
> > >
> > > Paul
> > >
> > > On 24 March 2015 at 18:06, Andre Vehreschild <vehre@gmx.de> wrote:
> > >> Hi all,
> > >>
> > >> I have worked on the comments Mikael gave me. I am now checking for
> > >> class_pointer in the way he pointed out.
> > >>
> > >> Furthermore did I *join the two parts* of the patch into this one,
> > >> because keeping both in sync was no benefit but only tedious and did not
> > >> prove to be reviewed faster.
> > >>
> > >> Paul, Dominique: I have addressed the LOC issue that came up lately. Or
> > >> rather the patch addressed it already. I feel like this is not tested
> > >> very well, not the loc() call nor the sizeof() call as given in the 57305
> > >> second's download. Unfortunately, is that download not runable. I would
> > >> love to see a test similar to that download, but couldn't come up with
> > >> one, that satisfied me. Given that the patch's review will last some
> > >> days, I still have enough time to come up with something beautiful which
> > >> I will add then.
> > >>
> > >> Bootstraps and regtests ok on x86_64-linux-gnu/F20.
> > >>
> > >> Regards,
> > >> Andre
> > >>
> > >>
> > >> On Tue, 24 Mar 2015 11:13:27 +0100
> > >> Paul Richard Thomas <paul.richard.thomas@gmail.com> wrote:
> > >>
> > >>> Dear Andre,
> > >>>
> > >>> Dominique pointed out to me that the 'loc' patch causes a ICE in the
> > >>> testsuite. It seems that 'loc' should provide the address of the class
> > >>> container in some places and the address of the data in others. I will
> > >>> put my thinking cap on tonight :-)
> > >>>
> > >>> Cheers
> > >>>
> > >>> Paul
> > >>>
> > >>> On 23 March 2015 at 13:43, Andre Vehreschild <vehre@gmx.de> wrote:
> > >>> > Hi Mikael,
> > >>> >
> > >>> > thanks for looking at the patch. Please note, that Paul has sent an
> > >>> > addendum to the patches for 60322, which I deliberately have attached.
> > >>> >
> > >>> >> 26/02/2015 18:17, Andre Vehreschild a écrit :
> > >>> >> > This first patch is only preparatory and does not change any of the
> > >>> >> > semantics of gfortran at all.
> > >>> >> Sure?
> > >>> >
> > >>> > With the counterexample you found below, this of course is a wrong
> > >>> > statement.
> > >>> >
> > >>> >> > diff --git a/gcc/fortran/expr.c b/gcc/fortran/expr.c
> > >>> >> > index ab6f7a5..d28cf77 100644
> > >>> >> > --- a/gcc/fortran/expr.c
> > >>> >> > +++ b/gcc/fortran/expr.c
> > >>> >> > @@ -4059,10 +4060,10 @@ gfc_lval_expr_from_sym (gfc_symbol *sym)
> > >>> >> > lval->symtree = gfc_find_symtree (sym->ns->sym_root, sym->name);
> > >>> >> >
> > >>> >> > /* It will always be a full array. */
> > >>> >> > - lval->rank = sym->as ? sym->as->rank : 0;
> > >>> >> > + as = sym->as;
> > >>> >> > + lval->rank = as ? as->rank : 0;
> > >>> >> > if (lval->rank)
> > >>> >> > - gfc_add_full_array_ref (lval, sym->ts.type == BT_CLASS ?
> > >>> >> > - CLASS_DATA (sym)->as : sym->as);
> > >>> >> > + gfc_add_full_array_ref (lval, as);
> > >>> >>
> > >>> >> This is a change of semantics. Or do you know that sym->ts.type !=
> > >>> >> BT_CLASS?
> > >>> >
> > >>> > You are completely right. I have made a mistake here. I have to tell
> > >>> > the truth, I never ran a regtest with only part 1 of the patches
> > >>> > applied. The second part of the patch will correct this, by setting
> > >>> > the variable as depending on whether type == BT_CLASS or not. Sorry
> > >>> > for the mistake.
> > >>> >
> > >>> >> > diff --git a/gcc/fortran/trans-decl.c b/gcc/fortran/trans-decl.c
> > >>> >> > index 3664824..e571a17 100644
> > >>> >> > --- a/gcc/fortran/trans-decl.c
> > >>> >> > +++ b/gcc/fortran/trans-decl.c
> > >>> >> > @@ -1013,16 +1017,24 @@ gfc_build_dummy_array_decl (gfc_symbol *
> > >>> >> > sym, tree dummy) tree decl;
> > >>> >> > tree type;
> > >>> >> > gfc_array_spec *as;
> > >>> >> > + symbol_attribute *array_attr;
> > >>> >> > char *name;
> > >>> >> > gfc_packed packed;
> > >>> >> > int n;
> > >>> >> > bool known_size;
> > >>> >> >
> > >>> >> > - if (sym->attr.pointer || sym->attr.allocatable
> > >>> >> > - || (sym->as && sym->as->type == AS_ASSUMED_RANK))
> > >>> >> > + /* Use the array as and attr. */
> > >>> >> > + as = sym->as;
> > >>> >> > + array_attr = &sym->attr;
> > >>> >> > +
> > >>> >> > + /* The pointer attribute is always set on a _data component,
> > >>> >> > therefore check
> > >>> >> > + the sym's attribute only. */
> > >>> >> > + if (sym->attr.pointer || array_attr->allocatable
> > >>> >> > + || (as && as->type == AS_ASSUMED_RANK))
> > >>> >> > return dummy;
> > >>> >> >
> > >>> >> Any reason to sometimes use array_attr, sometimes not, like here?
> > >>> >> By the way, the comment is misleading: for classes, there is the
> > >>> >> class_pointer attribute (and it is a pain, I know).
> > >>> >
> > >>> > Yes, and a good one. Array_attr is sometimes sym->attr and sometimes
> > >>> > CLASS_DATA(sym)->attr aka sym->ts.u.derived->components->attr. In the
> > >>> > later case .pointer is always set to 1 in the _data component's attr.
> > >>> > I.e., the above if, would always yield true for a class_array, which
> > >>> > is not intended, but rather destructive. I know about the
> > >>> > class_pointer attribute, but I figured, that it is not relevant here.
> > >>> > Any idea how to formulate the comment better, to reflect what I just
> > >>> > explained?
> > >>> >
> > >>> > Regards,
> > >>> > Andre
> > >>> > --
> > >>> > Andre Vehreschild * Email: vehre ad gmx dot de
> > >>> >
> > >>> >
> > >>> > ---------- Forwarded message ----------
> > >>> > From: Paul Richard Thomas <paul.richard.thomas@gmail.com>
> > >>> > To: Andre Vehreschild <vehre@gmx.de>, Dominique Dhumieres
> > >>> > <dominiq@lps.ens.fr> Cc:
> > >>> > Date: Sun, 22 Mar 2015 21:20:20 +0100
> > >>> > Subject: Bug in intrinsic LOC for scalar class objects
> > >>> > Dear Andre and Dominique,
> > >>> >
> > >>> > I have found that LOC is returning the address of the class container
> > >>> > rather than the _data component for class scalars. See the source
> > >>> > below, which you will recognise! A fix is attached.
> > >>> >
> > >>> > Note that the scalar allocate fails with MOLD= and so I substituted
> > >>> > SOURCE=.
> > >>> >
> > >>> > Cheers
> > >>> >
> > >>> > Paul
> > >>> >
> > >>> > class(*), allocatable :: a(:), e ! Change 'e' to an array and
> > >>> > second memcpy works correctly
> > >>> > ! Problem is with loc(e), which
> > >>> > returns the address of the
> > >>> > ! class container.
> > >>> > allocate (e, source = 99.0)
> > >>> > allocate (a(2), source = [1.0, 2.0])
> > >>> > call add_element_poly (a,e)
> > >>> > select type (a)
> > >>> > type is (real)
> > >>> > print *, a
> > >>> > end select
> > >>> >
> > >>> > contains
> > >>> >
> > >>> > subroutine add_element_poly(a,e)
> > >>> > use iso_c_binding
> > >>> > class(*),allocatable,intent(inout),target :: a(:)
> > >>> > class(*),intent(in),target :: e
> > >>> > class(*),allocatable,target :: tmp(:)
> > >>> > type(c_ptr) :: dummy
> > >>> >
> > >>> > interface
> > >>> > function memcpy(dest,src,n) bind(C,name="memcpy") result(res)
> > >>> > import
> > >>> > type(c_ptr) :: res
> > >>> > integer(c_intptr_t),value :: dest
> > >>> > integer(c_intptr_t),value :: src
> > >>> > integer(c_size_t),value :: n
> > >>> > end function
> > >>> > end interface
> > >>> >
> > >>> > if (.not.allocated(a)) then
> > >>> > allocate(a(1), source=e)
> > >>> > else
> > >>> > allocate(tmp(size(a)),source=a)
> > >>> > deallocate(a)
> > >>> > allocate(a(size(tmp)+1),source=e) ! mold gives a segfault
> > >>> > dummy = memcpy(loc(a(1)),loc(tmp),sizeof(tmp))
> > >>> > dummy = memcpy(loc(a(size(tmp)+1)),loc(e),sizeof(e))
> > >>> > end if
> > >>> > end subroutine
> > >>> > end
> > >>> >
> > >>>
> > >>>
> > >>>
> > >>
> > >>
> > >> --
> > >> Andre Vehreschild * Email: vehre ad gmx dot de
> > >
> > >
> > >
> > > --
> > > Outside of a dog, a book is a man's best friend. Inside of a dog it's
> > > too dark to read.
> > >
> > > Groucho Marx
> >
> >
> >
>
>
--
Andre Vehreschild * Email: vehre ad gmx dot de
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